JP7845772B2 - Ophthalmic device and focusing determination method - Google Patents

Description

This disclosure relates to an ophthalmic device and a method for determining focus.

Conventionally, slit-scan type fundus cameras (ophthalmic devices) for photographing the fundus of the eye under examination have been proposed. For example, Patent Document 1 describes a method in which a slit light (illumination light) irradiating the fundus using an optical scanner is moved, and the reflected light from the illumination area of the slit light moving within the fundus is captured by a CMOS image sensor with a rolling shutter function. This allows for the acquisition of a fundus image with reduced effects from scattered light.

Furthermore, Patent Document 2 describes an ophthalmic device that illuminates the fundus with a split index image and detects the reflected light of the split index from the fundus using a detector. Based on the detection results, the device evaluates and controls the focus of a fundus camera.

Patent No. 5736211 Patent No. 6518054

However, the ophthalmic devices described in Patent Documents 1 and 2 include separate illumination systems for evaluating the focus state and for observing the eye under examination. This is expected to increase the overall size and cost of the device.

In view of the above points, this disclosure aims to provide an ophthalmic device and a focusing determination method that enable observation of the eye under examination and evaluation of focus with a simple configuration.

To achieve the above-mentioned objectives, the ophthalmic apparatus according to this disclosure comprises: a spectroscopic member that spectrally separates light emitted from a light source into a first spectral component and a second spectral component; an optical scanner that guides the first spectral component and the second spectral component to the observation area of the eye under examination, which includes a plurality of imaging lines divided in the scanning direction; a line exposure type image sensor capable of detecting reflected light from the observation area and including a plurality of exposure lines in its light-receiving area, each corresponding to the imaging line and the imaging position; and a control unit that, while sequentially moving the exposure operation of a plurality of exposure lines included in a predetermined group of exposure lines, irradiates the regions of the plurality of imaging lines corresponding to the plurality of exposure lines in the group of exposure lines with the first spectral component and the second spectral component, and performs focus determination from the detection results of the exposure lines in the group of exposure lines.

To achieve the above-described objective, the focus determination method according to this disclosure is a method for determining focus in an ophthalmic apparatus comprising: a spectral member that spectrally separates light emitted from a light source into a first spectral spectrum and a second spectral spectrum; an optical scanner that guides the first spectral spectrum and the second spectral spectrum to an observation area of an eye under examination which includes a plurality of imaging lines divided in the scanning direction; and a line exposure type image sensor capable of detecting reflected light from the observation area and which includes a plurality of exposure lines in its light-receiving area, each corresponding to the imaging line and the imaging position, wherein the method includes the step of sequentially moving the exposure operation of a plurality of exposure lines included in a predetermined group of exposure lines, irradiating the regions of the plurality of imaging lines corresponding to the plurality of exposure lines in the group of exposure lines with the first spectral spectrum and the second spectral spectrum, and determining focus from the detection results of the exposure lines in the group of exposure lines.

According to the ophthalmic apparatus and focus determination method described herein, which utilize the above means, observation of the eye under examination and evaluation of focus can be performed with a simple configuration.

This is an overall configuration diagram of an ophthalmic device according to the present disclosure. This is a functional block diagram of the control unit. This is a schematic diagram of the optical path of an ophthalmic device, focusing on the optical path of light emitted from a spectral component. This is a schematic diagram of the optical path of an ophthalmic device, focusing on the optical path of light emitted from the first focusing optical system. This is a flowchart of the operation of an ophthalmic device. This image shows a lateral view of the area around the eye being examined, illustrating the optical path of the illumination light when the eye is in focus and when it is out of focus, and a frontal view of the fundus of the eye as seen from the front (direction P) when the illumination light is illuminating the eye. This figure shows a frontal view of the fundus, the light-receiving area of the image sensor, and the acquired image during focus adjustment. This chart shows the timing of the illumination light shining on the fundus of the eye during focus adjustment, as well as the timing of the exposure operation of the image sensor. This figure shows the relationship between the exposure line and the illumination light when the line is in focus and when it is out of focus. This image shows a lateral view of the area around the eye being examined, illustrating the optical path of the illumination light during focusing adjustment, and a frontal view of the fundus of the eye as seen from the front (direction P) with the illumination light shining on it. This figure shows a frontal view of the fundus, the light-receiving area of the image sensor, and the acquired image during focus adjustment. This figure shows a frontal view of the fundus, the light-receiving area of the image sensor, and the acquired image during slit-scan imaging. This chart shows the timing of the illumination light shining on the fundus during slit-scan imaging, as well as the timing of the exposure operation of the image sensor. This figure shows the relationship between the line profile and the modulation transfer function.

The embodiments of this disclosure will be described below with reference to the drawings. Figure 1 is an overall diagram of the ophthalmic apparatus 1. In Figure 1, the X direction is the left-right direction relative to the subject (the interocular width direction of the subject's eye E), the Y direction is the up-down direction, and the Z direction is the front-back direction relative to the subject (also called the working distance direction). Furthermore, in the following description of the ophthalmic apparatus 1, the devices and their arrangements are shown schematically and may differ from the actual scale for the sake of explanation.

The ophthalmic device 1 can perform slit-scan imaging of the fundus Ef of the eye E under examination. The ophthalmic device 1 comprises a main unit 11 that functions as a camera head, an operating unit 12, a display unit 13, and a control unit 14 (control unit).

The device body 11 is held by a drive mechanism (not shown) that allows it to be moved manually or automatically in the X, Y, or Z directions relative to the eye E being examined. Therefore, the device body 11 is configured to be moved relative to the eye E to allow for alignment adjustment.

The control unit 12 can receive input for various operations of the ophthalmic device 1, such as starting slit scan imaging, moving the device body 11 relative to the eye E under examination, and setting the ophthalmic device 1.

The display unit 13 can use a known display such as an LCD (Liquid Crystal Display). This display unit 13 displays the fundus image (frontal image) of the fundus Ef generated by the control device 14, as well as various setting screens.

The control device 14 is a computer or other processing unit that performs various calculation and control processes. The device body 11, the operation unit 12, and the display unit 13 are communicated to the control device 14. For example, the control device 14 comprehensively controls the operation of each part of the device body 11 and the display unit 13 based on operation instructions input to the operation unit 12. The control device 14 performs various controls and processes, including alignment of the device body 11, focus determination of the illumination system 2 and light receiving system 3 for the fundus Ef using the line profile 7 (see Figure 11, etc.), focus control of the first focus optical system 23 and the second focus optical system 31, slit scan imaging of the fundus Ef by the device body 11, and generation and display of the fundus image.

The configuration of the main unit 11 will now be described. The main unit 11 comprises an illumination system 2 and a light receiving system 3.

The illumination system 2 comprises a light source 21, a spectroscopic member 22, a first focusing optical system 23, multiple lenses (first illumination system lens 24, second illumination system lens 25, objective lens 53), an optical scanner 51, and an optical path splitting member 52. The first focusing optical system 23 and the area under observation (e.g., fundus Ef) are optically conjugate, and focusing is controlled by the control device 14 according to the relative position of the ophthalmic device 1 and the eye under examination E, and the position of the area under observation in the eye under examination E.

The light source 21 emits illumination light Ls. The light source 21 includes a light source element that emits visible light (e.g., white light) as illumination light Ls when slit scan imaging of the fundus Ef is performed, and near-infrared light (light in the infrared region), which has low visual sensitivity in the eye E under examination, when focusing adjustment is performed. The light source 21 may be composed of one or more light source elements. Visible light may also be used for focusing adjustment. As light source elements used in the light source 21, laser light-emitting elements, LEDs (Light Emitting Diodes), fluorescent light-emitting elements, etc., can be used.

The spectral member 22 has multiple circular splitting holes 221 arranged in the Y direction (also called the spectral direction) in Figure 1, and splits the light emitted from the light source 21. The spectral member 22 is located in an optically conjugate or substantially optically conjugate relationship with the anterior segment Ea (cornea and lens) of the eye E under examination, the optical scanner 51, and the optical path splitting member 52. The splitting holes 221 are arranged symmetrically with respect to the optical axis A, and in this embodiment, they are spaced apart at two locations in the Y direction in Figure 1 (see also Figure 3, etc.). By passing the illumination light Ls emitted from the light source 21 through the two splitting holes 221, the spectral member 22 can spectrally separate the illumination light Ls into a first spectral component (second component light Ls21) and another portion into a second spectral component (second component light Ls22).

The first focusing optical system 23 has a slit hole 231 that is irradiated by each light emitted from the spectral member 22. The slit hole 231 is formed in an elongated rectangular shape (see Figure 3). The slit hole 231 is positioned on the optical axis A so that it is elongated in the X direction. The first focusing optical system 23 is positioned in an optically conjugate or substantially optically conjugate relationship with the observed area of the eye E (fundus Ef in this embodiment). Therefore, the conjugate position with respect to the spectral member 22 is formed to be different from the conjugate position with respect to the first focusing optical system 23. The second focusing optical system 31 is provided so as to be movable along the optical axis B of the illumination light Ls (common axis with optical axis A from the eye E to the optical path dividing member 52), and the focus of the light receiving system 3 is adjusted by control by the control device 14. Note that the first focusing optical system 23 may have one or more lenses provided so as to be movable on either side or both sides of the slit hole 231 on the optical axis A, and the method of focus adjustment is not particularly limited.

The first illumination lens 24 focuses the illumination light Ls (first spectral portion (Ls21), second spectral portion (Ls22)) emitted from the slit hole 231 of the first focusing optical system 23 and guides it to the optical scanner 51.

The optical scanner 51 can be constructed using optical elements such as a galvanometer mirror, resonant mirror, polygon mirror, or MEMS (Micro Electro Mechanical System). It has a deflection function that allows it to deflect (scan) the illumination light Ls incident from the first illumination system lens 24 on the light source 21 side in one dimension, reflect it towards the subsequent second illumination system lens 25, and guide the light.

The deflection angle or direction of the illumination light Ls deflected by the optical scanner 51 is controlled by the control device 14. Furthermore, during slit scan imaging, the optical scanner 51 deflects the illumination light Ls in a direction perpendicular to both the optical axis A of the objective lens 53 (Z direction in Figure 1) and the long axis direction of the slit hole 231 (X direction in Figure 1) (Y direction in Figure 1). Therefore, the optical scanner 51 can guide the illumination light Ls emitted from the first focus optical system 23 to the observed area of the eye E (e.g., fundus Ef) in a movable illumination area R1.

The second illumination lens 25 focuses the illumination light Ls emitted from the optical scanner 51 and guides it to the optical path splitting member 52.

The optical path splitting member 52 is a so-called hall mirror, an annular reflective member having a substantially circular opening 521 that allows light to pass through to the inside. The optical path splitting member 52 reflects the illumination light Ls emitted from the second illumination system lens 25 and directs it toward the objective lens 53, while simultaneously allowing the reflected light Lb emitted from the objective lens 53 to pass through and guide it to the light receiving system 3. Note that the optical path splitting member 52 may be composed of mirrors or splitters of other shapes, as long as they can split the optical paths of the illumination light Ls and the reflected light Lb (i.e., guide the illumination light Ls toward the objective lens 53 on the eye E side and guide the reflected light Lb to the light receiving system 3).

The objective lens 53 illuminates a portion of the fundus Ef through the anterior segment Ea (cornea and lens) of the eye E being examined, reflecting the illumination light Ls from the optical path splitting member 52. At this time, the illumination light Ls is deflected in the Y direction by the aforementioned optical scanner 51, causing the elongated illumination light Ls (slit light) in the X direction to scan within the fundus Ef in the Y direction (scanning direction D1). While the illumination light Ls is being deflected in the Y direction, the reflected light Lb from the fundus Ef of the eye E being illuminated by the illumination light Ls is guided to the light receiving system 3 through the objective lens 53 and the optical path splitting member 52.

The light-receiving system 3 comprises an objective lens 53, an optical path splitting member 52, a second focus optical system 31, a light-receiving system lens 32, and an image sensor 33.

The second focusing optical system 31 includes one or more lenses (focusing lenses) that are movable along the optical axis B of the reflected light Lb (common to optical axis A from the eye E to the optical path splitting member 52), and adjusts the focus of the light receiving system 3 under control by the control device 14. The focusing of the light receiving system 3 by the second focusing optical system 31 and the focusing of the illumination system 2 by the first focusing optical system 23 are linked according to the diopter (diopter) of the eye E. The reflected light Lb that enters the second focusing optical system 31 from the optical path splitting member 52 enters the light receiving system lens 32. Note that instead of providing one or more movable focusing lenses in the second focusing optical system 31, one or more variable focus lenses may be provided, and the method of focus adjustment is not particularly limited.

The light-receiving lens 32 is composed of one or more lenses and focuses the reflected light Lb emitted from the second focus optical system 31 onto the image sensor 33.

The image sensor 33, for example, is a CMOS image sensor and is positioned to detect reflected light Lb from the observed area of the eye E under examination. The image sensor 33 has a light-receiving area 331 into which reflected light Lb from the light-receiving lens 32 enters, and has a rolling shutter function that detects (also called receiving or imaging) the reflected light Lb within this light-receiving area 331 while shifting the start and end timing of exposure for each predetermined exposure line 332. During slit scan imaging, the image sensor 33 is driven by the control device 14 to image the reflected light Lb of the illumination light Ls moving within the fundus Ef in accordance with the polarization of the illumination light Ls from the optical scanner 51, and outputs the imaging signal of the reflected light Lb to the control device 14.

Figure 2 is a functional block diagram of the control device 14. The functions of the control device 14 are realized using various processors. These various processors include CPUs (Central Processing Units), GPUs (Graphics Processing Units), ASICs (Application Specific Integrated Circuits), and programmable logic devices (e.g., SPLDs (Simple Programmable Logic Devices), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays)). Furthermore, the various functions of the control device 14 may be implemented by a single processor, or by multiple processors of the same or different types.

The control device 14 functions as an illumination control unit 141, a deflection control unit 142, an imaging control unit 143, a signal acquisition unit 144, an image generation unit 145, a focus evaluation unit 146, a repeat control unit 147, a focus control unit 148, and a display control unit 149 by executing a control program (not shown). Each functional unit of the control device 14 can be configured by software and/or hardware, or a combination thereof, through a program, circuit, device, or equipment.

Next, the optical path of illumination system 2 will be described. Figure 3 is a schematic diagram of the optical path of illumination system 2, focusing on the illumination light Ls (first component light Ls11, Ls12) passing through the spectral member 22. The top section shows a plan view 2-1, and the middle section shows a side view 2-2. The illumination light Ls emitted from the light source 21 is dispersed into multiple spectral components by the spectral member 22, with a portion exiting from one of the split holes 221 in the Y direction and another portion exiting from the other split hole 221 in the Y direction. Of the dispersed illumination light Ls, the spectral components guided with the split holes 221 of the spectral member 22 as the object point position will be described as the first component light Ls11, Ls12, and the spectral components guided with the slit hole 231 of the first focus optical system 23 as the object point position will be described as the second component light Ls21, Ls22.

In illumination system 2, the positions of the spectral element 22, optical scanner 51, optical path splitting member 52, and anterior segment Ea are optically conjugate or substantially conjugate to each other. The first component light Ls11 and Ls12, guided by the first illumination system lens 24, are substantially imaged on the reflective surface of the optical scanner 51 and reflected by the optical scanner 51 toward the second illumination system lens 25. Subsequently, the first component light Ls11 and Ls12 are guided by the second illumination system lens 25 toward the optical path splitting member 52, where they are substantially imaged on the annular reflective surface and reflected toward the objective lens 53. The first component light Ls11 and Ls12, focused by the objective lens 53, are imaged in the anterior segment Ea and then irradiated toward the fundus Ef.

In Figure 3 (and similarly in Figure 4), below the side view 2-2, the plan views of each optical component (spectroscopic component 22, first focus optical system 23, optical scanner 51, and optical path splitting component 52) are shown (viewed in the direction of optical axis A for the spectroscopic component 22 and the first focus optical system 23), and the cross-sectional shape of the illumination light Ls (second component light Ls21, Ls22) at optical path cross-sectional position S1 are shown.

Figure 4 is a schematic diagram of the optical path of illumination system 2, focusing on the illumination light Ls (second component light Ls21, Ls22) passing through the first focus optical system 23. In illumination system 2, the positions of the first focus optical system 23 and the fundus Ef (observed area) are optically conjugate or substantially conjugate to each other. The second component light Ls21, Ls22 emitted from the spectroscopic member 22 is guided by the first illumination system lens 24 and reflected by the optical scanner 51 toward the second illumination system lens 25. Subsequently, the second component light Ls21, Ls22 is guided by the second illumination system lens 25 to the optical path splitting member 52 and reflected toward the objective lens 53 by the reflective surface of the optical path splitting member 52. Furthermore, the second component light Ls21, Ls22 is re-imaged at the optical path cross-sectional position S1 between the optical path splitting member 52 and the objective lens 53. The second component light Ls21 and Ls22, focused by the objective lens 53, are focused in the anterior segment Ea and then irradiated onto the fundus Ef. In the fundus Ef, the second component light Ls21 and Ls22 are substantially re-imaged. In this way, the illumination system 2 allows the optical scanner 51 to guide the illumination light Ls, which is the second component light Ls21 (first spectral component) and the second component light Ls22 (second spectral component), to a portion of the fundus Ef, which is the observation area 61, and irradiate it as slit light.

Note that while Figure 4 shows the optical path where illumination system 2 is in focus, the position of the eye E under examination may vary each time ophthalmic device 1 is used. Therefore, ophthalmic device 1 can be adjusted to adjust its focus, as described later.

Figure 5 is an operation flowchart of the ophthalmic device 1. In step S01, the ophthalmic device 1 is activated by the user via a power switch (not shown) or the like, which activates the hardware (HW) and software (SW).

In step S02, the control device 14 switches to the shooting mode upon receiving an instruction to switch to the shooting mode from the operation unit 12. Also, in step S03, the control device 14 adjusts the working distance (WD) of the eye E being examined based on instructions from the operation unit 12.

In step S04, the control device 14 performs focus adjustment (also called "focus alignment") of the illumination system 2 and the light-receiving system 3. Here, the focus is adjusted to the fundus Ef as the area to be observed. In this embodiment, the ophthalmic device 1 performs focus adjustment, including focus evaluation and control of the illumination system 2 and the light-receiving system 3 relative to the fundus Ef, before the slit scan imaging of the fundus Ef performed in step S05. In the focus evaluation, attention is paid to the change in the width of the illumination area R1 (light image) of the illumination light Ls relative to the fundus Ef between the state where the illumination system 2 and the light-receiving system 3 are in focus (focused) and the state where the illumination system 2 and the light-receiving system 3 are not in focus (out-of-focus).

Figure 6 shows side views 6A1-6A3 of the area around the eye E under examination, indicating the optical path of the illumination light Ls in both focused and out-of-focus states, and front views 6B1-6B3 of the observed region 61 of the fundus Ef, viewed from the front (P direction) of the eye E under examination when illuminated by the illumination light Ls.

As shown in the side view 6A1, when in focus, the focusing positions of the light beams of each spectral component (second component light Ls21, Ls22) coincide (or nearly coincide) with the fundus Ef. Therefore, as shown in the front view 6B1, one second component light Ls21 and the other second component light Ls22 overlap at approximately the same position in the Y direction (scanning direction of the optical scanner 51), and the illumination light Ls is irradiated onto the slit-shaped illumination region R1. On the other hand, as shown in the side views 6A2, 6A3 and the front views 6B2, 6B3, when out of focus, the focusing positions of the light beams of each spectral component (second component light Ls21, Ls22) shift anterior-posterior (optical axis A direction) relative to the fundus Ef. Therefore, the second component light Ls21 (first spectral component) and the second component light Ls22 (second spectral component) irradiate the illumination region R1 which is spread (shifted) in the Y direction on the fundus Ef.

For example, as shown in the side view 6A2, when the illumination light Ls is imaged in front of the fundus Ef, as shown in the front view 6B2, one of the second component lights Ls21 is illuminated downwards and the other second component light Ls22 is illuminated upwards compared to when it is in focus (front view 6B1). On the other hand, as shown in the side view 6A3, when the illumination light Ls is imaged behind the fundus Ef, as shown in the front view 6B3, one of the second component lights Ls21 is illuminated upwards and the other second component light Ls22 is illuminated downwards compared to when it is in focus (front view 6B1). The amount of displacement of the image formation positions of the second component lights Ls21 and Ls22 relative to the fundus Ef (the amount of displacement in the optical axis A direction) can be evaluated from the light intensity I of the illumination light Ls, which correlates with the amount of displacement of the second component lights Ls21 and Ls22 in the Y direction in the front views 6B1 to 6B3. In the example shown in Figure 6, the light intensity I of the illumination light Ls illuminating the illumination region R1 when it is in focus (as shown in front view 6B1) is higher than the light intensity I of the illumination light Ls illuminating the illumination region R1 when it is out of focus (as shown in front view 6B2 or 6B3).

Figure 7 shows a front view 6B4 of the fundus Ef, the area to be observed during focus adjustment, the light-receiving area 331 of the image sensor 33, and the acquired image 71 obtained by imaging the fundus Ef with the image sensor 33.

The frontal view 6B4 of the fundus Ef shows the illumination light Ls focused at a position above the optical axis A (above the Y-axis). The frontal view 6B4 of the fundus Ef shows the observation area 61. The observation area 61 includes multiple imaging lines 611 divided in the scanning direction D1 of the illumination light Ls. Multiple imaging lines 611 are formed, numbered N=1 to N=n (where "n" is an integer greater than or equal to 2). Note that the imaging lines 611 are hypothetical regions illustrated for illustrative purposes.

The image sensor 33, composed of a CMOS image sensor or the like, has a light-receiving area 331 that has multiple photodiodes arranged in a matrix in the vertical and horizontal directions to provide light. The image sensor 33 has a rolling shutter function and is a line exposure type image sensor that includes multiple exposure lines 332 in the light-receiving area 331, each corresponding to the imaging line 611 and the imaging position. The light-receiving area 331 has multiple exposure lines 332 divided in the exposure direction D2. The exposure lines 332 are unit areas that detect light received in the light-receiving area 331 at the same timing. The exposure lines 332 have multiple light-receiving units arranged in a row direction perpendicular to the exposure direction D2 in the light-receiving area 331 shown in Figure 7. In addition, the exposure lines 332 have one or more light-receiving units for the exposure direction D2 in the light-receiving area 331. Multiple exposure lines 332 are formed, numbered N=1 to N=n (where "n" is an integer of 2 or more). The imaging lines 611 with line numbers N=1 to n correspond to the imaging positions of the exposure lines 332 with line numbers N=1 to n.

The acquired image 71 is an image formed by the reflected light Lb that is incident on the light-receiving area 331 of the image sensor 33 and detected. The acquired image 71 includes a dark region 712 in which the light intensity I of the light detected in the light-receiving area 331 is relatively low, and a bright region 711 in which the light intensity I of the detected illumination light Ls corresponding to the illumination area R1 is high. The control device 14 obtains a line profile 7 as a detection result, which corresponds the light intensity I of the acquired image 71 obtained by the image sensor 33 to the detection direction D3. The line profile 7 shows the high and low levels of light intensity I with respect to the detection direction D3, which has the same movement direction as the scanning direction D1 and exposure direction D2, and includes a first detection value p corresponding to the bright region 711 and a second detection value v corresponding to the dark region 712. In the example of Figure 7, since the illumination light Ls is relatively close to being in focus with respect to the fundus Ef, the intensity ratio of the first detection value p to the second detection value v is relatively high. In this embodiment, the control device 14 calculates the visibility V = (p - v) / (p + v) using the first detected value p at the peak of the light intensity I and the second detected value v at the bottom of the line profile 7, and evaluates the focus state (degree of focus or out of focus). For example, the control device 14 determines that focus is achieved if the visibility V = (p - v) / (p + v) is equal to or greater than a predetermined threshold.

Figure 8 shows the timing chart for the illumination light Ls irradiating the fundus Ef during focus adjustment and the timing chart for the exposure operation of the image sensor 33. The timing characteristic F1 for the illumination light Ls moves the position of the imaging line 611 in the scanning direction D1 (see Figure 7) as time T progresses. In the example in Figure 8, illumination light Ls (first spectral and second spectral) is irradiated at line numbers N=2 and N=8 of the imaging line 611, respectively, between timing T0 and timing T3 and between timing T6 and timing T9, and the illumination light Ls is stopped (turned off) between timing T3 and timing T6. Although Figure 8 shows an example in which illumination light Ls is irradiated intermittently in two time regions (between timing T0 to T3 and between timing T6 to T9), illumination light Ls is similarly irradiated intermittently during the period from timing T9 to timing Tn. Therefore, the exposure line group 333 for detecting the second component light Ls21 (first spectral distribution) and the second component light Ls22 (second spectral distribution) is also provided intermittently (see also Figure 11).

Furthermore, the timing characteristic F2 for the exposure operation of the image sensor 33 sequentially moves the position of the exposure line 332 in the exposure direction D2 (see Figure 7) as time T progresses. In the example in Figure 8, in each interval from timing T0 to timing T10, the exposure operation is performed using the exposure line 332 from line number N=1 to line number N=10. Similarly, in each period from timing T10 to timing Tn, the exposure line 332 sequentially moves from line number N=11 to N=n, and the exposure operation is performed.

As described above, when the illumination light Ls is irradiated and the exposure operation is performed, during the period when the multiple exposure lines 332 are in exposure operation (for example, from timing T0 to timing T3), the illumination light Ls is irradiated to the approximate center position of the multiple imaging lines 611, each of which corresponds to the imaging position of each exposure line 332 (for example, if the line numbers N of the imaging lines 611 are "1" to "3", then the imaging line 611 with the central line number N=2). In this embodiment, the group including the multiple exposure lines 332 used for evaluating the focus of the illumination light Ls is referred to as the exposure line group 333.

As shown in Figure 8, the control device 14 sequentially moves the exposure operation of multiple exposure lines 332 included in a predetermined exposure line group 333 in the exposure direction D2, while irradiating the illumination area R1 of the multiple imaging lines 611 corresponding to the multiple exposure lines 332 in the exposure line group 333 with illumination light Ls (first spectral portion (Ls21) and second spectral portion (Ls22)). In this embodiment, the control device 14 (control unit) performs focus determination by obtaining the line profile 7 described above from the detection results of the exposure lines 332 in the exposure line group 333.

Figure 9 shows a specific example of the relationship between the exposure line 332 and the illumination light Ls when in focus or out of focus. First, as shown in the light-receiving region 331 in the focused state, the exposure line group 333 in this embodiment is provided along the optical path from the first focus optical system 23, which is the origin (object point) of the illumination light Ls, to the image sensor 33, with an angle width of 3 degrees in the exposure direction D2. Furthermore, in the focused state, the second component light Ls21 and Ls22 reaching the light-receiving region 331 arrive along the optical axes A and B from the first focus optical system 23 to the image sensor 33, with an angle width of 1.5 degrees in the exposure direction D2.

Receiving example A1 shows the illumination light Ls in focus. In receiving example A1, the illumination light Ls is irradiated with a width of approximately 1.5 [deg] that fits within the exposure line group 333. Receiving example A2 shows the illumination light Ls out of focus. In receiving example A2, the illumination light Ls is in a state where the separation of the second component light Ls21 and Ls22 has progressed, and it is irradiated with a width that is wider in the exposure direction D2 (up and down direction in Figure 9) within the exposure line group 333 than in receiving example A1, and slightly narrower than the exposure line group 333. Receiving example A3 shows the illumination light Ls out of focus. In receiving example A3, the illumination light Ls is separated into the second component light Ls21 and Ls22 and irradiated so as to straddle both boundaries in the width direction of the exposure line group 333. The light intensity I (first detection value p) of the illumination light Ls detected by the light-receiving area 331 is smallest in the order of reception example A1, reception example A2, and reception example A3. In this way, by setting the width of the exposure line group 333 to be wider than the width of the illumination light Ls when in focus, the illumination light Ls can be detected even when the widths of the second component light Ls 21 and Ls 22 are widened and the light is out of focus, as long as it is within the width range of the exposure line group 333.

Note that the width of the exposure line group 333 ("3 [deg]") and the width of the illumination light Ls ("1.5 [deg]") are examples. As shown in light reception example A1, the width of the exposure line group 333 may be set to a width greater than the width of the illumination light Ls at the time of focus.

Figure 10 shows side views 6A5-6A7 of the area around the eye E, indicating the optical path of the illumination light Ls, and front views 6B5-6B7 of the fundus Ef, viewed from the front (direction P) of the eye E illuminated by the illumination light Ls, during focus evaluation imaging. The control device 14 changes the deflection angle of the illumination light Ls from the optical scanner 51 and captures the reflected light Lb from the fundus Ef illuminated by the illumination light Ls using the image sensor 33, acquiring the acquired image 71. Then, based on the line profile 7 obtained from the acquired image 71, the control device 14 performs focus control of the first focus optical system 23 and the second focus optical system 31 so that the visibility V is maximized.

Focus evaluation and control are primarily performed by the illumination control unit 141, deflection control unit 142, imaging control unit 143, signal acquisition unit 144, image generation unit 145, focus evaluation unit 146, repeat control unit 147, and focus control unit 148 of the control device 14 shown in Figure 2.

The illumination control unit 141 emits illumination light Ls (e.g., near-infrared light) from the illumination system 2 during focus evaluation. When near-infrared light is used as the illumination light Ls, pupillary constriction of the eye E under examination can be reduced.

During focus evaluation, the signal acquisition unit 144 sequentially acquires the imaging signal output from the light-receiving area 331 of the image sensor 33 while the rolling shutter of the image sensor 33 is being driven.

The image generation unit 145 generates the acquired image 71 based on the imaging signal acquired by the signal acquisition unit 144 while the rolling shutter of the image sensor 33 is being driven during focus evaluation. As shown in Figure 6, in the observed area 61 when in focus (see front view 6B1), the illumination light Ls is detected as a narrow pattern image, and in the observed area 61 when out of focus (see front views 6B2 and 6B3), the illumination light Ls is detected as a widened or separated pattern image.

The focus evaluation unit 146 controls the optical scanner 51 via the illumination control unit 141 and the image sensor 33 via the imaging control unit 143 to perform image acquisition. For example, the focus evaluation unit 146 uses the deflection control unit 142 to control the deflection angle of the illumination light Ls from the optical scanner 51 so that the illumination light Ls is irradiated onto the fundus Ef. Furthermore, the focus evaluation unit 146 obtains a line profile 7 from the acquired image 71 and performs a focus evaluation based on the line profile 7.

The repeat control unit 147 performs repeat control, repeatedly activating the focus evaluation unit 146, signal acquisition unit 144, and image generation unit 145 for each of several different positions of the first focus optical system 23, while changing the lens position of the focus lens of the first focus optical system 23 and the second focus optical system 31. This acquires an image 71 for each position of the first focus optical system 23. If the first focus optical system 23 and the second focus optical system 31 are equipped with a variable focus lens instead of a focus lens, the repeat control unit 147 performs repeat control for each of several different focal positions of the variable focus lens.

The focusing control unit 148 controls the focusing of the first focusing optical system 23 and the second focusing optical system 31 to focus the illumination system 2 and the light-receiving system 3 on the fundus Ef. As mentioned above, the focusing of the light-receiving system 3 by the second focusing optical system 31 and the focusing of the illumination system 2 by the first focusing optical system 23 move in conjunction with the diopter (visual intensity) of the eye E being examined. Based on the line profile 7 obtained from the acquired image 71, the focusing control unit 148 controls the first focusing optical system 23 and the second focusing optical system 31 so that the visibility V is maximized (i.e., so that the state is closest to the in-focus state).

Thus, when the first focusing optical system 23 focuses on the area to be observed in the eye E (fundus Ef in this embodiment), the second focusing optical system 31 controls the focusing of the image sensor 33 in conjunction with the focusing of the first focusing optical system 23 so that the area to be observed and the image sensor 33 are in focus. The control device 14 can evaluate the focusing state and control the focusing by having the image sensor 33 detect the illumination area R1 of the illumination light Ls (second component light Ls21, Ls22) on the fundus Ef and evaluating the line profile 7.

As shown in Figure 11, the focus evaluation unit 146 can obtain a line profile 7 from the acquired image 71 which includes a plurality of bright regions 711 obtained according to the timing chart in Figure 8, and evaluate the focus state by calculating the visibility V from this line profile 7. The focus evaluation unit 146 may perform the focus evaluation based on a line profile 7 which includes a first detected value p corresponding to one bright region 711, or it may perform the focus evaluation based on a line profile 7 which includes first detected values p corresponding to two or more bright regions 711. When the control device 14 uses a line profile 7 which includes two or more bright regions 711, it can determine that the position of the bright region 711 with the highest first detected value p among the plurality of bright regions 711 is the position that is most in focus. Therefore, the control device 14 can determine, for example, that if a bright area 711 with a high first detection value p is observed approximately in the center of the fundus Ef, it determines that the focal point is located on the far side of the entire fundus Ef, which is the observed area 61. Conversely, if a bright area 711 with a high first detection value p is observed at the beginning or end of the scanning direction D1 in the fundus Ef, it determines that the focal point is located on the near side of the entire fundus Ef, which is the observed area 61. This allows the control device 14 to determine whether the focal point needs to be moved to the near or far side of the fundus Ef to achieve focus.

Returning to Figure 5, in step S05, the control device 14 performs slit-scan imaging. During slit-scan imaging, the illumination control unit 141, deflection control unit 142, imaging control unit 143, signal acquisition unit 144, image generation unit 145, and display control unit 149 of the control device 14 shown in Figure 2 primarily function.

The illumination control unit 141 controls the emission of illumination light Ls from the light source 21 (i.e., the illumination system 2). During slit scan imaging, the illumination control unit 141 emits visible light as illumination light Ls from the light source 21.

The deflection control unit 142 controls the deflection angle of the illumination light Ls from the optical scanner 51. During slit scan imaging, the deflection control unit 142 controls the optical scanner 51 to deflect the illumination light Ls in the Y direction, thereby scanning the fundus Ef in the Y direction (for example, the scanning direction D1 from top to bottom) using the illumination light Ls (slit light).

As shown in Figure 12, the illumination area R1 of the illumination light Ls moves in the Y direction within the fundus Ef (observed area) in accordance with the Y-direction deflection of the illumination light Ls (see also the side views 6A5-6A7 and front views 6B5-6B7 in Figure 10). Note that in Figure 12, the illumination area R1 of the illumination light Ls is shown to be approximately the same width as the imaging line 611, but it may be wider than the imaging line 611. Furthermore, as shown in Figure 13, in accordance with the movement of this illumination area R1, the exposure line 332 of the reflected light Lb within the light-receiving area 331 also moves synchronously in the exposure direction D2 (Y direction).

The imaging control unit 143 controls the drive of the image sensor 33. During slit-scan imaging, the imaging control unit 143 causes the image sensor 33 to perform a rolling shutter drive while the illumination light Ls from the optical scanner 51 is being deflected in the Y direction (i.e., while the illumination area R1 moves in the scanning direction D1 within the fundus Ef).

Specifically, the imaging control unit 143 tracks the exposure line 332 in accordance with the illumination area of the reflected light Lb moving in the scanning direction D1 within the light-receiving area 331, and continuously detects the reflected light Lb using the exposure line 332. In other words, as the illumination area R1 moves in the scanning direction D1 within the fundus Ef, the image sensor 33 locally tracks the exposure range, and continuous detection of the illumination area R1 is performed. Since known techniques can be used for such rolling shutter driving, a detailed explanation is omitted.

The signal acquisition unit 144 is connected to the image sensor 33 via a communication interface (not shown) either by wire or wireless connection. During slit-scan imaging, the signal acquisition unit 144 sequentially acquires the imaging signal (also called the detection signal or reception signal) from the light-receiving area of the image sensor 33 while the illumination light Ls is being deflected by the optical scanner 51.

The image generation unit 145 can generate a fundus image based on the imaging signal acquired by the signal acquisition unit 144 while the illumination light Ls is being deflected by the optical scanner 51 during the slit scan imaging described above. The acquired image 71 in Figure 12 shows a state where an image partially representing the fundus Ef has been generated by superimposing the light detected by the exposure lines 332 with line numbers N=1 and N=2.

In step S06, the display control unit 149 controls the display by the display unit 13. For example, during slit-scan imaging, the display control unit 149 displays the fundus Ef image generated by the image generation unit 145 on the display unit 13.

In step S07, the control device 14 determines whether to perform a reshoot. If a reshoot is performed ("Reshoot Required" in step S07), the control device 14 executes the process in step S02; otherwise, it executes the process in step S08. Note that in step S07, the control device 14 may also determine whether a reshoot is required or not based on a selection instruction entered by the user into the operation unit 12. The user can determine whether a reshoot is required or not by checking the acquired image displayed on the display unit 13.

In step S08, the control device 14 stores the acquired images from the slit scan imaging, which are obtained as imaging results, in a storage unit (or memory device) not shown.

In step S09, the control device 14 proceeds to the next imaging (for example, imaging another eye E) according to the input instructions to the operation unit 12.

The ophthalmic device 1 of this embodiment has been described above, but the ophthalmic device 1 may also have a function to determine the modulation transfer function (MTF). Figure 14 is a diagram showing the relationship between the line profile 7 and the modulation transfer function F3.

The modulation transfer function F3 represents the visibility V [au] for each spatial frequency [Line/mm] of the bright region 711 and dark region 712 periodically detected in the acquired image 71. The control device 14 can determine the modulation transfer function F3 by pre-determining the visibility V in the in-focus state at multiple spatial frequencies f01 to f03 (by increasing or decreasing the number of exposure lines 332 included in the exposure line group 333, and the spacing between multiple exposure line groups). The modulation transfer function F3 represents the relationship between the ideal state visibility V of an optical system with certain performance and the spatial frequency. Since the visibility V at a certain spatial frequency is measured while being affected by the optical system of the eye E (including the cornea, lens, etc.), it does not reach the ideal state visibility V even when in focus on the eye E (fundus Ef). The light projected onto the eye E is captured by the image sensor 33 via the optical system having the modulation transfer function F3.

The difference between the visibility V measured under the ideal state described above and the visibility V obtained through actual measurement can be interpreted as the change due to the optical system (cornea, lens, etc.) of the eye E being examined. Therefore, by pre-determining the modulation transfer function F3, the control device 14 can measure the parameters of the modulation transfer function F3 related to the eye E being examined.

Furthermore, the control device 14 can also use the contrast level of the modulation transfer function F3 (for example, the difference between the visibility V measured as an ideal state and the visibility V obtained by actual measurement) as a clue to determine whether the image is in focus (in focus) on the eye E being examined. Therefore, by using the modulation transfer function F3, focus determination can be made easier.

Furthermore, the control device 14 can determine an appropriate visibility threshold V for focus determination for each spatial frequency from the line profile 7 obtained at a specific spatial frequency. The visibility threshold V for focus determination can be set manually or automatically. With this configuration, the control device 14 can increase or decrease the number of exposure lines 332 included in the exposure line group 333, and the spacing between multiple exposure line groups, to determine focus based on multiple line profiles 7.

As described above, in this embodiment, a spectroscopic member separates the light emitted from the light source 21 into a first spectral component (Ls21) and a second spectral component (Ls22), an optical scanner 51 guides the first spectral component (Ls21) and the second spectral component (Ls22) to the observed area 61 of the eye E, which includes a plurality of imaging lines 611 divided in the scanning direction D1, and a light receiving area 3 that can detect the reflected light Lb from the observed area 61 and has a plurality of exposure lines 332 whose imaging positions correspond to the imaging lines 611. The configuration of the ophthalmic apparatus 1 was described, comprising a line exposure type image sensor 33 included in 31, and a control device 14 (control unit) that, while sequentially moving the exposure operation of multiple exposure lines 332 included in a predetermined exposure line group 333, irradiates the regions of multiple target lines 611 corresponding to the multiple exposure lines 332 of the exposure line group 333 with first spectral (Ls21) and second spectral (Ls22) and performs focus determination from the detection results of the exposure lines 332 in the exposure line group 333.

This configuration reduces the number of optical components needed to split the illumination light Ls (for example, it is not necessary to provide a separate prism or the like in addition to the spectral component 22 as an optical component for splitting the illumination light Ls in the illumination system 2). The illumination system 2, including the light source 21, can be used for both the light source and optical path for focus evaluation and the light source and optical path for observation. Therefore, an ophthalmic device 1 and a focus determination method that enable observation and focus evaluation of the eye E under examination can be constructed with a simple configuration.

This concludes the description of the embodiments of this disclosure. However, the embodiments of this disclosure are not limited to the configurations shown in each embodiment.

For example, in this embodiment, the split holes 221 of the spectral member 22 are shown as being spaced apart in two locations in the Y direction of Figure 1. However, multiple split holes 221 may be provided at eccentric positions with respect to the optical axis A, and the number and arrangement of the split holes 221 may be in other configurations.

Furthermore, the spectroscopic member 22, the first focus optical system 23, and the image sensor 33 may be configured to rotate synchronously around optical axes A and B. In this case, for example, the reflective surface of the optical scanner 51 can be configured to be arbitrarily tilted in two axial directions (for example, directions around two axes perpendicular to each other with respect to the optical axis). This allows the scanning direction of the illumination light Ls relative to the fundus Ef, which is the area to be observed, to be set to an arbitrary direction, or the orientation of the slit-shaped illumination light Ls (for example, the orientation of the illumination light Ls in the longitudinal direction) to be changed. Therefore, by illuminating the illumination light Ls from different angles to the illumination area R1, observation of the area to be observed can be performed with higher precision. In addition to the spectroscopic member 22, the first focus optical system 23, and the image sensor 33, the optical scanner 51 may also be rotated synchronously (for example, around the normal to the reflective part (reflective surface) of the optical scanner 51) so that the scanning direction of the illumination light Ls relative to the fundus Ef and the orientation of the illumination light Ls change.

Furthermore, the first spectral spectrum (Ls21) and the second spectral spectrum (Ls22) may be irradiated as spectrally separated light with different characteristics. For example, by making the wavelengths of the first spectral spectrum (Ls21) and the second spectral spectrum (Ls22) different, the proximity position of the device body 11 relative to the observed area can be evaluated according to the vertical position of the first spectral spectrum (Ls21) and the second spectral spectrum (Ls22) irradiated onto the object under observation. The control device 14 can determine that the device body 11 is far from the observed area if the first spectral spectrum (Ls21) of the illumination light Ls irradiated onto the fundus Ef, which is the observed area, is located below the second spectral spectrum (Ls22) (front view 6B2 in Figure 6), and can determine that the device body 11 is far from the observed area if the first spectral spectrum (Ls21) is located above the second spectral spectrum (Ls22) (front view 6B3 in Figure 6). Furthermore, as a spectral method in which the wavelengths of the first spectral analysis (Ls21) and the second spectral analysis (Ls22) are different, for example, a dichroic filter can be placed in the divided hole 221 of the spectral element 22 only during focus evaluation.

1 Ophthalmic device 2 Illumination system 3 Light receiving system 6A1-6A3, 6A5-6A7 Side view 6B1-6B9 Front view 7 Line profile 11 Device body 12 Operation unit 13 Display unit 14 Control device 21 Light source 22 Spectroscopic member 23 First focus optical system 24 First illumination system lens 25 Second illumination system lens 31 Second focus optical system 32 Light receiving system lens 33 Image sensor 51 Optical scanner 52 Optical path splitting member 53 Objective lens 61 Observed area 71 Acquired image 141 Illumination control unit 142 Deflection control unit 143 Imaging control unit 144 Signal acquisition unit 145 Image generation unit 146 Focus evaluation unit 147 Repeat control unit 148 Focus control unit 149 Display control unit 221 Split hole 231 Slit hole 331 Light receiving area 331A Light receiving area 332 Exposure line 333 Exposure line group 521 Aperture 611 Imaging line 711 Bright area 712 Dark area A Optical axis B Optical axis D1 Scanning direction D2 Exposure direction D3 Detection direction E Eye under examination Ea Anterior segment Ef Fundus F1 Timing characteristic F2 Timing characteristic F3 Modulation transfer function I Light intensity Lb Reflection light Ls Illumination light Ls11 First component light Ls12 First component light Ls21 Second component light (first spectrum)
Ls22 Second component light (second spectroscopy)
N Line number R1 Irradiation area S1 Optical path cross-sectional position V Visibility f01-f03 Spatial frequency p First detection value v Second detection value

Claims (5)

A spectroscopic component that separates light emitted from a light source into a first spectral component and a second spectral component,
An optical scanner that guides the first spectral line and the second spectral line to the observation area of the eye to be examined, which includes multiple imaging lines divided in the scanning direction,
A line exposure type image sensor capable of detecting reflected light from the observed area, and including a plurality of exposure lines in the light-receiving area, each corresponding to the imaging line and the imaging position,
A control unit that, while sequentially moving the exposure operation of a plurality of exposure lines included in a predetermined group of exposure lines, irradiates the regions of the plurality of lines to be imaged corresponding to the plurality of exposure lines in the group of exposure lines with the first spectral and the second spectral, and performs a focus determination from the detection results of the exposure lines in the group of exposure lines,
Equipped with,
The control unit,
As a result of the detection, a line profile is obtained that corresponds the light intensity of the image acquired by the image sensor to the detection direction.
In the aforementioned line profile, focus is determined to be achieved when the visibility V = (p - v) / (p + v), which is calculated using the first detected value p at the peak of the light intensity and the second detected value v at the bottom, is equal to or greater than a predetermined threshold.
Ophthalmology equipment. The ophthalmic apparatus according to claim 1, wherein the group of exposure lines for detecting the first and second spectral components is provided intermittently. The ophthalmic apparatus according to claim 2, wherein the control unit increases or decreases the number of exposure lines included in the exposure line group and the spacing between the multiple exposure line groups, and evaluates focus based on the multiple line profiles. A spectroscopic component that separates light emitted from a light source into a first spectral component and a second spectral component,
An optical scanner that guides the first spectral line and the second spectral line to the observation area of the eye to be examined, which includes multiple imaging lines divided in the scanning direction,
A line exposure type image sensor capable of detecting reflected light from the observed area, and including a plurality of exposure lines in the light-receiving area, each corresponding to the imaging line and the imaging position,
A control unit that, while sequentially moving the exposure operation of a plurality of exposure lines included in a predetermined group of exposure lines, irradiates the regions of the plurality of lines to be imaged corresponding to the plurality of exposure lines in the group of exposure lines with the first spectral and the second spectral, and performs a focus determination from the detection results of the exposure lines in the group of exposure lines,
Equipped with,
The control unit is an ophthalmic device that increases or decreases the number of exposure lines included in the exposure line group and the spacing between the multiple exposure line groups, and evaluates focus based on multiple line profiles. A spectroscopic component that separates light emitted from a light source into a first spectral component and a second spectral component,
An optical scanner that guides the first spectral line and the second spectral line to the observation area of the eye to be examined, which includes multiple imaging lines divided in the scanning direction,
A line exposure type image sensor capable of detecting reflected light from the observed area, and including a plurality of exposure lines in the light-receiving area, each corresponding to the imaging line and the imaging position,
A method for determining focus in an ophthalmic device equipped with the following features:
The process includes sequentially moving the exposure operation of a plurality of exposure lines included in a predetermined group of exposure lines, irradiating the regions of the plurality of lines to be imaged corresponding to the plurality of exposure lines in the group of exposure lines with the first spectral and the second spectral, and performing a focus determination from the detection results of the exposure lines in the group of exposure lines,
The control unit is
As a result of the detection, a line profile is obtained that corresponds the light intensity of the image acquired by the image sensor to the detection direction.
In the aforementioned line profile, focus is determined to be achieved when the visibility V = (p - v) / (p + v), which is calculated using the first detected value p at the peak of the light intensity and the second detected value v at the bottom, is equal to or greater than a predetermined threshold.
Focus determination method.